Advances in modem medical imaging technologies such as X-ray, ultrasound, or magnetic resonance imaging make it possible to identify and to biopsy tumors while they are still small. When dealing with a small tumor, especially after a portion of the tumor has been removed for biopsy, it is sometimes difficult to relocate the tumor at a later time for treatment. This is particularly true in the case of tumors in the breast, where the ability to visualize a small growth may depend upon the manner in which the breast is positioned or compressed during the procedure. In addition, prior to surgically removing a tumor, it is often advantageous to try to shrink the tumor by chemotherapy or irradiation. This is especially true in the case of breast cancer, where conservation of breast tissue is a concern. Shrinkage of the tumor can sometimes make it difficult for the surgeon to locate the tumor.
A solution to this problem is to place a marker within the target tissues at the time of biopsy which can be visualized under a variety of imaging modalities to facilitate finding the tumor at a later time. When a suspicious mass is detected, a sample is taken by biopsy, often, but not necessarily, using a specialized instrument such as a biopsy needle. The needle is inserted in the breast while the position of the needle is monitored using fluoroscopy, ultrasonic imaging, X-rays, MRI or other suitable imaging modalities.
In a new procedure, called stereotactic needle biopsy, the breast is compressed between the plates of a mammography apparatus and two separate X-rays are taken from different points of reference. The exact position of the mass or lesion is calculated within the breast. The coordinates of the lesion are then programmed into a mechanical stereotactic apparatus which guides the biopsy needle to the lesion.
Irrespective of the biopsy technique, the surgical site may need to be examined or accessed for surgical treatment of a cancerous lesion. Treatment requires the surgeon or radiologist locate the lesion precisely and this may need to be done repeatedly over a period of time. Since treatment may alter the host tissue, the function of a marker even more important.
U.S. Pat. No. 6,725,083 for “Tissue site markers for in vivo imaging” describes biopsy site markers and methods that permit conventional imaging techniques to be used, such as ultrasonic imaging. The biopsy site markers have high ultrasound reflectivity due to high contrast of acoustic impedance resulting from gas-filled internal pores. The markers may have a non-uniform surface. The patent discloses the use of materials such as metal, ceramic materials, metal oxides, polymer, and composites and mixtures thereof.
U.S. Pat. No. 6,350,244 for “Bioabsorable markers for use in biopsy procedure” discloses a breast tissue marker that allows the marker to be left in place avoiding the need for surgical removal. One type of marker takes the form of hollow spheres made of polylactite acid filled with iodine or other radiopaque material to make them visible under X-rays and/or ultrasound. The radiopaque materials are also bioabsorbable. Another type of marker disclosed is a solid marker of pre-mixed radiopaque material and a bioabsorbable material. The solid markers may also include dyes and radioactive materials.
U.S. Pat. No. 6,347,241 for “Ultrasonic and x-ray detectable biopsy site marker and apparatus for applying it” shows a biopsy site marker of small bodies or pellets of gelatin which enclose substantially a radioopaque object. The pellets are deposited at the biopsy site by an applicator device inserted in the biopsy site. Several gelatin pellets are deposited through the tube. The radio opaque core in the gelatin bodies are of a non-biological material and structure which are readily identified during X-ray observations.
U.S. Pat. No. 6,161,034 for “Methods and chemical preparations for time-limited marking of biopsy sites” describes markers that remain present to permit detection and location of the biopsy site. The markers are later absorbed by the host. The patent discloses gelatin, collagen, balloons and detectability provided by AgCl; Agl; BaCO3; BaSO4; K; CaCO3; ZnO; Al2O3; and combinations of these.
US Patent Publication No. 2006/0079805 for “Site marker visible under multiple modalities” describes site markers that include balls or particles which are bonded together to form a marker body. The balls or particles are made from biocompatible materials such as titanium, stainless steel or platinum. The balls or particles are described as being bonded together by sintering or by adhesive such as epoxy. An alternative embodiment has at least one continuous strand of wire of biocompatible material such as titanium, stainless steel, platinum, or other suitable material, compressed to form a mass that resembles a ball of yarn. Another alternative is a resonating capsule, or a rod with drilled holes.
US Patent Publication No. 2006/0036165 for “Tissue site markers for in vivo imaging” shows ultrasound-detectable markers whose shapes are distinct in an image from biological shapes. Various shapes are disclosed including cylinders, coils, and other more complex shapes.
US Patent Publication No. 2005/0234336 for “Apparatus and method for marking tissue” describes permanent biopsy markers that support visualization under multiple modalities such as MRI, X-ray and ultrasound. The marker has a body made of a resilient, preferably non-absorbable polymer material that is radiopaque and echogenic. The material expands in situ. The materials for the marker include polyacrylates, ethylene-vinyl acetates (and other acyl-substituted cellulose acetates), polyurethanes, polystyrenes, polyvinyl oxides, polyvinyl fluorides, poly(vinyl imidazoles), chlorosulphonated polyolefins, polyethylene oxides, polyvinyl alcohols (PVA), polytetrafluoroethylenes and nylons, with the preferred material being polyvinyl alcohol (PVA) and alkylated or acylated derivatives thereof.
U.S. Pat. No. 5,676,146 shows an implant used to repair skeletal defects and irregularities. The implant is of radiolucent material and with a resorbable radiopaque marker, such as nondemineralized or partially demineralized bone particles. A radiopaque component, which is resorbable in its entirety, is included. Examples of materials include demineralized bone sheet, particles, etc., collagen and collagen derivatives, plastic such as polyethylene cetabular cups.
Collagen has been proposed as a material for implants and various methods of preparation and types of materials are known. Examples are disclosed in U.S. Pat. Nos. 5,800,541; 5,162,430; 5,328,955; and 5,475,052
It is believed that most known tissue markers have a disadvantage in that they are not visible under all available imaging modalities. The features of a marker that make it stand out under X-rays do not necessarily make them stand out under MRI or ultrasound imaging. One prior art mechanism for addressing the need for multiple-imaging-mode markers is to employ a combination of metal structure and biodegradable foam to provide ultrasonic imaging visibility, MRI visibility and x-ray visibility. In this case, the metal structure provides x-ray visibility and biodegradable foam provides visibility in ultrasonic imaging.
There is a need for site markers made from biocompatible materials that are visible under various modes of imaging to reduce the number of procedures that patients must undergo in detection and treatment of cancer or any disease requiring the user of tissue markers. It will be a valuable contribution to the art for a marker with a simple design and superior biocompatibility can be provided.